
HALO-BLIGHT OF OATS 



BY 



CHARLOTTE ELLIOTT 



Reprinted from JOURNAL OF AGRICULTURAL RESEARCH 

Vol. XIX, No. 4 : : : : : Washington, D. C, May 15, 1920 



mi 




PUBLISHED BY AUTHORITY OF THB SECRETARY OF AGRICULTURE, WITH 
THE COOPERATION OF THB ASSOCIATION OF LAND-GRANT COLLEGES 



WASHINGTON » GOVERNMENT PRINTING OFFICE : 1920 



LIBRARY OF CONGRESS 

APR 6 1922 



-o^oft 



bj u* 



HALO-BLIGHT OF OATS 1 

By Charlotte Elliott 

Scientific Assistant, Laboratory of Plant Pathology, Bureau of Plant Industry, 
United States Department of Agriculture 

INTRODUCTION 

The present paper is a description and discussion of a bacterial disease 
of oats which has been the subject of investigation by the writer for the 
past three years. This "halo-blight" is a disease which occurs to at 
least some extent each year throughout the oat-growing sections of the 
central and eastern States and becomes of economic importance during 
certain seasons when weather conditions are particularly favorable to 
its development. 

During the season of 191 8 field observations and specimens of 
diseased plants from widely separated sections of Wisconsin showed 
that this disease occurred in practically all the oat fields of the State 
and was responsible for the abnormal condition prevalent in the early 
part of that season. 

DESCRIPTION OF HALO-BLIGHT LESIONS 

The halo-blight is most conspicuous on the leaves (PI. C; 26), although 
it may occur on leaf sheaths and glumes (Pi. 29) . Typical well-developed 
lesions of the disease are oval chlorotic spots ^ to 2 cm. or more 
in diameter about points of infection which consist of gray-brown col- 
lapsed tissue measuring from 1 to several millimeters in length. The 
halolike border is at first only slightly lighter green than the surrounding 
tissue, but as it becomes older it loses more of its green color and forms 
oval yellow halos about the central infection areas. 

Lesions are first visible as light green oval spots 4 to 5 mm. in diameter 
with central sunken points of infection at first evident only on one side 
of the leaf. This center of infection increases slowly in size, penetrates 

1 The greater part of this work was carried on at the University of Wisconsin during 1917 and 1918 
under the direction of Prof. L. R. Jones and was continued in the Pathological Laboratory of the United 
States Department of Agriculture during 1918 and 1819 under the direction of Dr. Erwin F. Smith. The 
writer also wishes to acknowledge the courtesy of the Boston Branch of the Association of Collegiate 
Alumnae whose research fellowship she held during the college year of 1917-18. 



Journal of Agricultural Research, Vol. XIX, No. 4 

Washington, D. C Ma V J 5- ^ 2 ° 

uc Key No. G-191 

(139) 



140 Journal of Agricultural Research voi.xrx, No. 4 

the leaf tissue, and in a day or two forms a gray or brown dry tissue from 
1 to several millimeters in diameter, evident on both sides of the leaf 
blade. The halolike margin spreads rapidly, becoming uniformly 
lighter green to yellow or showing concentric markings (PI. 26) of 
different shades of green and yellow. Occasionally these halolike 
margins are prolonged at one end into points (PI. C) from 1 to several 
centimeters long. They may extend as yellow streaks through the 
center or along the margin to the tip of the leaf, but ordinarily they 
appear as oval spots, measuring 1 cm. or more in diameter. Marginal 
infections are common, forming crescent-shaped lesions. These halo- 
like lesions are conspicuous and characteristic. Except in the central 
infection area the tissues remain turgid and have a normal appearance 
except for the paler yellowish color. There is no water-soaked margin 
about the halo as described by Wolf and Foster (io) 1 for similar lesions 
of the wildfire disease of tobacco, and the spots do not fall out of the 
leaves. Exudate does not occur in connection with the lesions. When 
several lesions occur on the same leaf they often coalesce and produce a 
general yellowing followed by a breaking across of leaf blades (PI. C) or 
a shriveling and drying of tips and margins. During periods of warm, 
dry weather yellow haloed leaf tissue loses its turgidity and color and 
forms oval, gray-brown dead spots which on some leaves have narrow, 
brown margins and on others narrow, yellow halolike margins. Very 
rarely the dead tissue may assume a pinkish or reddish brown color. In 
separate lesions the oval outline of the dead halo persists, and even when 
the whole leaf becomes dry and brown, the original halo outlines may 
still be distinguished. 

PREVALENCE AND GEOGRAPHICAL DISTRIBUTION 

Personal observations in Wisconsin and specimens of diseased plants 
from Ohio, Illinois, Indiana, Minnesota, Tennessee, California, and 
Virginia have led to the conclusion that halo-blight is present in oat fields 
every season, scattered lesions occurring on the lower leaves more or less 
throughout the season and occasionally attacking the panicles. These 
lesions on the lower leaves are more or less hidden by the fresher upper 
leaves and so escape observation. Only under particularly favorable 
weather conditions does the blight develop sufficiently to attract 
attention or to do serious damage. 

FIELD WORK IN 1918 

During the season of 191 8 weather conditions favorable to halo-blight 
prevailed in Wisconsin and parts of adjoining States, causing an un- 
usually severe bacterial blighting. In the experimental plots, halo 
lesions began to appear on from 1 to 25 per cent of the young plants 
about the middle of May. By May 25 practically every plant showed 

1 Reference is made by number (italic) to "Lirerature cited," p. 172. 



May 15.19*0 Halo-Blight of Oats 141 



some spotting. During the last week in May and the first week in June 
all untreated plots looked yellowed or slightly browned when viewed 
from a distance. Practically every first leaf and half of the second 
leaves were yellowed and dead. Many leaves had yellowed, shriveled 
tips and margins, and single lesions were abundant on the upper leaves 
of many varieties. 

Every field about Madison showed some blighting. Usually the 
brown, dead leaves were easily seen from the road, and 100 per cent of 
infection was not at all uncommon. Some fields south of Madison 
showed distinct yellow spots from a yard to a rod or more in diameter. 
One field of oats near Monroe, Wis., visited May 29, was so badly 
blighted as to show from a distance a general yellowing with scattered 
patches of more marked yellow. Closer examination showed abundant 
halo lesions, every plant being infected. About 3 per cent of the plants 
were yellowed throughout, the outer leaves were water-soaked and dead, 
and some whole plants were stunted to such an extent that their recovery 
seemed doubtful. On the remaining 97 per cent of the plants the outer 
two to three leaves were collapsed and dead, and the others showed 
scattered halo lesions in varying stages of development. Where the blight 
was farther advanced the leaves were broken over and the tips shriveled 
and brown. Other leaves showed typical, conspicuous, isolated halo 
lesions which were central or marginal, covering one-half to the entire 
width of the leaf blade. The plants in this field showed no marked red- 
dening. They had been badly beaten by recent driving storms. Two 
other oat fields in the vicinity showed a normal stand, but the halo-blight 
was abundant. No plants remained uninfected, but nevertheless none 
were stunted or entirely yellowed, and chances for recovery were much 
better than for the field described above. The blight was general through- 
out the section about Monroe, and the two fields last mentioned probably 
represented the average. This yellowed condition of oat fields in this 
section was first evident May 26 and was reported by a number of farmers. 
From May 3 1 to June 2 oat fields were visited by the writer in five coun- 
ties of southern Wisconsin. More than 130 fields were inspected, and 
every one showed halo-blight varying in amount from a fraction of 1 per 
cent to 100 per cent, the latter being much the more common. The 
amount varied not only in individual fields but also conspicuously in 
different counties. 

In Jefferson County 26 fields were visited. The oats were about half 
grown. One-fourth of the fields showed only scattered lesions on the 
lower leaves— an infection of 1 per cent or less. About one-half of the 
fields showed a general spotting of the lower leaves on from 60 to 100 per 
cent of the plants. In some cases the infection was in patches from 2 
to 6 feet in diameter, where every plant had all but the last one or two 
leaves badly spotted. A few fields showed general and heavy infection 
of 100 per cent of the plants. Even the upper leaves were spotted. 



142 Journal of Agricultural Research vol. xix, No. 4 

The lower leaves were mostly gone, but a general yellowing of the fields 
was not marked. Only one field was so seriously affected as to show 
heavy general blighting and large yellow spots 1 to 3 rods across. About 
60 per cent infection of the lower leaves was typical for the fields through- 
out this section. 

In Dodge County the halo-blight was much more abundant. Of the 
37 fields visited all showed at least 20 per cent infection; 5 showed light 
infection — spotting of the lower leaves of 20 to 50 per cent of the plants. 
This infection, however, was evident from the road. Over half of these 
fields showed heavy infection — 60 to 100 per cent — on at least the lower 
leaves, and yellowed spots in the fields. The plants in these yellowed 
spots had little normal green leaf area, and as many as 10 per cent of the 
plants were entirely yellow and stunted. About one-third of the fields 
showed 100 per cent infection of the lower leaves, the browned tips and 
margins showing plainly and often giving a brownish tinge to the fields. 
In two fields the lower two to three leaves were practically dead and the 
upper leaves so badly spotted as to give a general yellow color to the 
fields. In all fields visited in Dodge County blight was evident without 
a close examination and was sufficiently severe to threaten the crop if 
unfavorable weather conditions continued. New green leaves were just 
beginning to appear. 

In Fond du Lac County, farther north, the plants were smaller — 6 to 8 
inches high — and the blight was not heavy in most fields. Seven fields 
showed only traces of blight on lower leaves — 1 to 30 per cent. One 
showed 100 per cent infection on the lower leaves and another heavy 
infection — 100 per cent — and a general yellowing of the field. 

In Columbia and Sauk Counties 10 fields showed a normal blue-green 
color but had 20 to 100 per cent infection on the lower leaves. Ten other 
fields showed yellow spots or a general yellowing of the fields. This 
section was second to Dodge County in the amount of bacterial blight. 

Reports and specimens of plants from 35 counties in Wisconsin showed 
that leaf lesions were general throughout the oat-growing sections of the 
State and that a single disease, the halo-blight, was responsible for the 
trouble. A similar condition was reported for the oat fields of southern 
Minnesota, Iowa, northern Illinois, and Indiana. 

For several years previous to 191 8 this bacterial blight was observed 
in Wisconsin oat fields, but there was never enough of it to attract par- 
ticular attention. The cool, cloudy days and frequent rains of the 1918 
oat season proved to be just the conditions necessary to favor the develop- 
ment and spread of the disease. The average rainfall for May, 191 8, 
was 6.66 inches, or considerably more than the normal for that month 
and greater than for any year since 1892. At Madison there were only 
four clear days during the month, and at least four heavy rainstorms 
were accompanied by strong, driving winds especially favorable to the 
spread of the disease. During June the weather conditions were much 



May 15, 1920 



Halo-Blight of Oats 



143 



less favorable for the spread of the bacterial blight. The total precipi- 
tation in Wisconsin for June was 2.31 inches, or below normal, while the 
average temperature increased from 58. i° F. in May to 63.9 in June. 

With this rise in temperature and decrease in rainfall reports came in 
of improved conditions in the oat fields. The new leaves which came 
out were unspotted, and by the last of the month all the fields had resumed 
a normal color and appeared to have almost completely recovered. The 
badly yellowed field near Monroe was visited again July 2. It had 
resumed a normal green color throughout with no halo lesions on the 
upper leaves and only scattered old lesions lower down. The stand was 
thin and the plants smaller than in adjoining fields. Neighboring fields 
were just heading out, but this field would be 10 days to 2 weeks late. 
Other fields showing yellow spots were reported to have resumed a normal 
color, but plants in spots previously yellowed were at least a week behind 
the others in development. This change of weather conditions in June 
came at an opportune time. Continued cloudy, rainy weather would 
undoubtedly have destroyed many plants and reduced the yield. As it 
was, reports for the two seasons of 1917 and 191 8 show an increase per 
acre for the whole State of 2.2 bushels in 1918, but this increase would 
undoubtedly have been more than doubled but for the presence of halo- 
blight. Following the unusually severe bacterial blight of the early part 
of the season, blasting of panicles was also unusually abundant and gen- 
eral throughout Wisconsin oat fields during 1918. In extreme cases as 
many as 25 to 50 per cent of the spikelets in a head were undeveloped. 
Counts of 30 panicles in a severely blighted spot gave an average of 29 
spikelets per panicle and 31 per cent blasting. Counts of 30 panicles 
from a part of this same plot not severely halo-blighted gave an average 
of 34 spikelets per panicle and 20 per cent blasting. 

On six panicles sent in from Lincoln County the numbers of normal and 
blasted spikelets were as follows : 



Panicle 
No. 


Number of 

normal 
spikelets. 


Number of 

blasted 
spikelets. 


I 
2 

3 
4 
5 
6 


36 
24 
38 
IO 
34 
16 


2S 

°34 

28 

8 

20 

19 



1 Top blasted. 

The blasted spikelets are mostly in the lower half of the panicle, but 
occasionally the upper half is blasted as in No. 2. 

All the experimental plots showed considerable blasting and numerous 
empty spikelets. Counts of 36 panicles of Wisconsin No. 14 oats from 
treated seed showed an average of 1 1 per cent of the spikelets blasted, 



144 Journal of Agricultural Research vol. xix.no. 4 

varying from o to 30 per cent. Counts of 40 similar panicles showed 21 
per cent of the spikelets blasted. Experiments carried on during the 
summer of 1918 indicate that this blasting is probably not due to the 
bacterial disease but to the unusual meteorological conditions which 
favored the development and spread of the bacterial blight. 

BACTERIAL ISOLATION EXPERIMENTS 

Oat plants showing typical lesions of halo-blight were collected from 
fields around Madison, Wis., and from other points in the State, from 
Tennessee, Urbana, 111., Lafayette, Ind., Wooster, Ohio, Davis, Calif., 
and Arlington Farm, Va. Twenty-eight isolations were made from these 
lesions, and 36 isolations from halo lesions produced by inoculations 
in the field and greenhouse. Most of these isolations were from leaf 
lesions, but a few were made from lesions on glumes (PI. 29). 

The first isolations were made by washing the leaf tissue through 10 
sterile water blanks, crushing on a sterile slide, transferring to broth, and 
plating from this broth suspension. Later isolations were made by 
dipping the tissue for a second in 95 per cent alcohol, then into 1 to 1,000 
mercuric chlorid (HgCl 2 ) for one minute, washing through three sterile 
water blanks, and proceeding as in the earlier method. This later method 
proved to be more satisfactory, but a comparison of the results from 
both methods proved interesting. 

From all these isolations, with the exception of two from glumes, typi- 
cal white colonies of the halo organism were obtained. These appeared 
on potato agar in from 1 to 3 days. When the first method of isolation 
was used, without sterilizing the surfaces of the tissues, yellow colonies 
appeared on the plates with the white colonies in 25 per cent of the 
isolations from natural infections and in 22 per cent of the isolations 
from inoculation experiments. When the surfaces of the lesions were 
sterilized in mercuric chlorid for one minute no yellow colonies were 
obtained. Twelve isolations were made from natural infections, using 
mercuric chlorid ; and a still larger number were made from lesions due to 
inoculation experiments. One set of isolations was made by placing the 
leaf tissue in the mercuric chlorid for only 30 seconds. This leaf tissue 
had been sprayed with a mixed culture of yellow and white organisms. 
Yellow colonies appeared on the plates with the white colonies, but the 
yellow colonies were not nearly so numerous as on plates poured from, 
tissue which had not been sterilized If the tissue had remained in the 
mercuric chlorid for 60 seconds instead of 30 seconds no yellow colonies 
would have appeared. These yellow organisms appear to be surface 
saprophytes and do not occur within the tissues. 

The yellow colonies were mostly of one kind, judged by their appear- 
ance on agar plates — round, smooth, shining, lemon-yellow with entire 
margins — and they appeared on the potato agar in from one to two days. 
This type of colony was chosen for inoculation experiments. 



May is, iswo Halo-Blight of Oats 145 

The white colonies of halo-producing organisms from natural infections 
were all alike on beef-peptone agar, but on potato agar two only of the 
man}/ isolations gave colonies of a slightly different character, like that 
designated in this paper as "stock. " 

On potato agar most of the isolations gave raised, umbonate colonies 
of a butyrous consistency with thin margins, entire or slightly undu- 
late. This was the usual type of colony isolated. The two varying 
isolations were from a leaf lesion from Lafayette, Ind., and a glume lesion 
on Wisconsin No. 14 oats in an experimental plot. (See PI. 31, C; 32, A.) 
The colonies were thicker and of an equal thickness out to the margin; 
the margin was slightly undulate, and the consistency of the colony 
was like that of boiled starch or gelatin. They gave a more rapid 
and abundant growth on potato agar than the common type. This 
second type of colony is the same as an isolation made in 191 6 by Mr. 
Reddy from a halo lesion on oats and kept as a stock culture at Madison, 
Wis. 

The pathogenicity of each of these 28 isolations from natural infec- 
tions was tested and proved by one or more inoculation experiments. 
Mr. Reddy's oat stock culture and isolation No. 36 (the common form) 
from a leaf lesion from Wooster, Ohio, were used as representatives of 
the two types of white colonies in the inoculation and cultural work and 
are designated respectively as "stock" and "36." 

INOCULATION EXPERIMENTS 

1. Inoculation experiments were carried on at Madison, Wis., in 
experimental plots out of doors and in the greenhouses. The plants in 
the field were in various stages of development, from half gro^ra to fully 
headed; and those in the greenhouse were from 4 to 8 inches high. The 
uninjured plants were sprayed with water suspensions of organisms from 
agar slants 2 days to 1 week old. The greenhouse plants were then 
placed in damp chambers for 48 hours. Plants sprayed in the field were 
covered with water-proofed translucent (glassine) bags for the same 
length of time. Control plants were sprayed with sterile water and 
treated in the same manner. Oat plants of Wisconsin No. 1, Wis- 
consin No. 5, and Wisconsin No. 14 were used for greenhouse inocula- 
tions. Wisconsin No. 14 was used more often than the others because 
it proved to be more susceptible than any other variety. Occasionally 
halo lesions appeared at the end of the first 48 hours, when the plants 
were removed from the damp chamber; but usually none appeared until 
3 to 4 days after inoculation. On young plants the lesions were often 
so numerous that centers of infection appeared in rows where the organ- 
isms had entered the stomata. The halolike discolorations around 
these points of sunken tissue were at first only slightly lighter green 
than the normal tissue but quickly became more marked until about a 
week after inoculation, when the tissue was a distinct yellowish green 



146 Journal of Agricultural Research vol. xix.No. 4 

to yellow. Numerous confluent lesions quickly killed the leaf tips and 
margins, which shriveled, turned brown, and died. Isolated lesions de- 
veloped in the same way into distinct oval spots of yellow tissue 1 cm. 
or more in diameter with small dead centers. Infection was always 
abundant on inoculated oat plants. (See PI. 27.) 

Cultures proved by inoculation experiments to be pathogenic were 
kept as stock cultures. In this way 21 such cultures were obtained. 

2. Since both yellow and white colonies were isolated from leaf sec- 
tions showing halo lesions, inoculations were made with pure cultures 
of each and also with mixed cultures of yellow and white colonies for 
comparison with inoculation work done by Thomas F. Manns (3, p. 107, 
PL I). In 25 inoculation experiments pure cultures of the white halo 
organisms produced abundant and typical infections. In 13 tests, pure 
cultures of the yellow organisms produced no lesions whatsoever. 
Twelve sets of inoculations were made with mixed cultures by com- 
bining the 2 white halo organisms, No. 36 and stock, with 4 different 
isolations of yellow organisms. Isolation 39a from a leaf lesion from 
Urbana, 111., was the yellow organism most often used. Separate pure 
cultures of yellow and white organisms were used for control inocula- 
tions. The cultures were mixed just before the inoculations were made 
for the reason that long-continued attempts to grow mixed cultures in 
broth or on various agars were not successful. 1 In the 12 inoculation 
tests with the yellow and white mixed cultures typical halo infections 
were produced, but the lesions were only one-half to three-fourths as 
abundant as on plants inoculated with pure cultures of the white 
organisms. The development of lesions from mixed cultures was also 
somewhat retarded, the infections being evident from one to two days 
later than tnose obtained from the pure white cultures. These inoculation 
experiments showed plainly that the white organism alone is responsible 
for the production of the halo lesions while the yellow organisms used 
are neither parasites nor favorable to parasitism. 

3. In June, 191 8, field inoculations were made on the following 13 
Wisconsin varieties: Wisconsin No. 1, 3, 4, 5, 7, 13, 14, 15, 22, 25, 49, 
52, and 62. The plants were just beginning to head out, and the experi- 
ment was carried on to test the pathogenicity of the white organisms on 
mature leaves and on panicles, and the effects of possible lesions upon 
the development of the panicles, spikelets, and kernels. Water suspen- 
sions of the halo organisms were sprayed into unopened sheaths upon 
uninjured bundles of plants, the tops of which were drawn together and 
tied close so as to be covered with bags, and upon bundles of plants 

1 For two months mixed cultures of white and yellow organisms were grown on potato agar and in +10 
beef-peptone broth. Plates poured from these cultures when they were 5 days old showed a few white 
and many yellow organisms in the broth cultures and about equal numbers of yellow and white on agar. 
Plates poured from these cultures ?% weeks later showed no growth of either white or yellow colonies from 
the agar and showed pure cultures of the yellow organisms from the broth. On the contrary, separate 
pure cultures of the same organisms held for the same time in these media and under the same conditions 
gave abundant and characteristic colonies on the plates poured. 



May is, 19=0 Halo-Blight of Oats 147 

injured with a scalpel or drawn between the fingers to rub off the bloom. 
Bundles of control plants were treated in the same manner and sprayed 
with sterile water. All inoculated and control plants were covered with 
glassine bags for 48 hours, as stated above. Characteristic halo lesions 
appeared on all the varieties inoculated except Wisconsin No. 4. Only 
uninjured plants of this variety were inoculated. Five other varieties 
(No. 22, 25, 49, 52, and 62) showed no lesions on uninjured plants, but 
all varieties showed fairly abundant spotting of leaves and sheaths of 
plants which had had the bloom removed or had been cut with a scalpel. 
Some of these leaves were almost entirely yellowed with lesions. On 
6 varieties lesions appeared on uninjured plants, but the lesions were not 
nearly so abundant as on injured leaves and panicles. Wisconsin No. 7 
was the only variety in which the panicles were entirely out of the 
sheaths. In this variety every spikelet of the injured panicles showed 
halo lesions which stood out as oval yellow spots on the glumes. About 
half of the spikelets in these panicles were not filled out. Spikelets of 
untreated panicles of the same variety were also poorly filled out. Under 
favorable conditions the panicles appear to be just as susceptible to halo- 
blight as the leaves. Wisconsin No. 14 also showed heavy spotting of 
injured panicles. Uninjured spikelets of two varieties were halo-spotted 
when the suspension was sprayed into the unopened sheath. 

Though none of the controls showed any halo lesions, both water- 
sprayed controls and inoculated plants showed considerable sterility, 
amounting to from one-fifth to one-half of the spikelets in a panicle. 
Untreated heads of the same varieties and in the same plots showed either 
no sterility at all or only traces at the base of the panicle. This sterility 
was particularly abundant when either the water suspension or sterile 
water was sprayed into unopened sheaths or sheaths just opening at the 
top. The fact that both controls and inoculated plants showed the same 
amounts of sterility would indicate that the sterility was not due to the 
effects of the organism. Excessive moisture around the developing 
spikelets while these were still inclosed within the sheath offers the most 
plausible explanation for this sterility. In the same way heavy rains at 
the time oat fields are heading out probably account for the sterility 
commonly observed in oat fields. This set of field inoculations has led 
to the following conclusions : 

1. Leaves and panicles of oat plants approaching maturity are sus- 
ceptible to halo infection under favorable conditions. 

2. Infection takes place more readily on injured than on uninjured 
parts of the plants. 

3. Some varieties are more susceptible to infection than others. Green- 
house inoculations on young plants also led to this conclusion. 

4. Although both natural and artificial halo infection may occur on 
heads, these infections are not responsible for the blasting of oat heads. 
Sterility is due probably to physiological rather than pathological con- 
ditions. 



148 Journal of Agricultural Research voi.xix.No. 4 

CULTURAL CHARACTERS 
I. — STOCK HALO ORGANISM 

Morphology. — The organism is a motile rod with rounded ends (PI. 
34, B, E), sometimes occurring singly or paired, but usually in short 
to long chains (PI. 34, C). Organisms grown on beef-peptone agar and 
potato agar and stained with Ribbert's capsule stain, gentian violet, and 
carbol fuchsin measure from 1 to 4 fx in length and from 0.4 to 0.8 n in 
width, with an average of 0.65 by 2.3 /x. Stained by the Van Ermengen 
method from 24-hour cultures on beef-peptone agar, the organism shows 
from one to several polar flagella about the same length as the organism 
or only a little longer (PI. 34, E). No spores have been observed, 
although special staining methods with hot carbol fuchsin and methylene 
blue were used. Capsules are formed on both potato and beef-peptone 
agar and were stained with Ribbert's capsule stain (PI. 34, D). Compact 
pseudozoogloeae are not formed — that is, there is little or no viscidity. 
No branched forms have been observed. 

Nutrient broth. — Beef-peptone bouillon ( + 10) shows light clouding 
in 24 hours at 25 C. In 5 days there is moderate uniform clouding, 
and a flocculent white film or pellicle forms on the surface and falls to the 
bottom of the tube in small white flakes. On further shaking the flakes 
disappear. In older cultures there may be no pellicle but merely a slight 
ring around the surface. The clouding is never very heavy, and the thin 
surface film soon disappears. The medium is gradually changed in color 
until at the end of 60 days it is a deep amber brown. 1 The odor of decay 
is distinct with more or less of the penetrating smell of ammonia. The 
sediment in cultures from recent isolations is loosely flocculent. There 
was a somewhat viscid swirl in some of the old broths containing sodium 
chlorid. Rectangular crystals form at the surface. 

Broth plus absolute alcohol. — To 10 cc. of +15 beef- peptone 
bouillon absolute alcohol was added to make 4, 5, 6, and 7 per cent. 
There was heavy clouding in 4 and 5 per cent, moderate clouding in 6 per 
cent, and slight clouding in two out of three tubes of 7 per cent. 

Agar stroke. — On + 10 beef-peptone agar slants growth in 2 days is 
moderate, flat, undulate, white, shining, translucent, slightly contoured, 
butyrous. The medium is slightly browned. There is a slight odor of 
decay. 

On potato-dextrose agar slants the growth in 2 days is abundant, 
slightly undulate, raised, glistening, smooth, opaque, white, of gelatinous 
consistency (PI. 30, B, b). The medium is unchanged and there is no odor. 

Agar colonies. — (1) On poured plates of +10 2 beef-peptone agar 
from + 10 broth cultures, colonies appear after 30 hours at 25 C. as tiny 
translucent dots. When 2 days old the colonies are 1 to 2 mm. in diame- 

1 Ridgway, Robert, color standards and color nomenclature. 43 p., 53 col. pi. Washington, 
D.C. 1912. 
8 Fuller's scale. 



May 15, i 9 :o Halo-Blight of Oats 149 

ter, white, smooth, shining, round, with a denser center. When 11 days 
old they are more or less irregularly circular, 5 to 10 mm. in diameter in 
thin-sown plates, and flat with slightly raised margins. Microscopically, 
-.nth low powers, the internal structure is filamentous, the margin consist- 
ing of folded parallel strands or chains. The margin is undulate. Deep 
colonies are lens-shaped and opaque. The medium may be slightly 
browned. The markings in Plate 31, A, B, E, F, are characteristic of 
these colonies under a hand lens, and they do not disappear as the colonies 
grow older. Very similar markings appear in young colonies of some of 
the softrot organisms. A half dozen of these softrot organisms tried on 
oats have not produced an}' halo lesions. 

(2) On plates of potato-dextrose agar the colonies grow more rapidly. 
They are raised, white, shining, opaque, with only slightly undulate or 
entire margins, and of the same gelatinous consistency described above 
(Pl. 3 i,C; 32, A.) 

Gelatin colonies. — Growth slow, circular, crateriform, margins en- 
tire to undulate with folded strands (PI. 31, G), liquefaction saucer-shaped, 
rather slow. 

Gelatin stab. — Growth on + 10 peptone gelatin at 22 C. is slow, best 
at the top, with only a slight filiform growth along line of stab, liquefaction 
crateriform. At the end of 2 days a small pit is formed at the surface 
3 mm. deep. At the end of 6 days liquefaction extends two-thirds of the 
way across a 20-mm. tube, and the pit is 10 mm. deep. At the end of 18 
days liquefaction covers the surface to a depth of 14 mm. At the end 
of 60 days (at 20 ) the tube is only half liquefied. 

Potato cylinders. — At 25 C. there is moderate growth in 24 hours 
and slight darkening of the medium. At the end of 4 days growth is 
abundant, flat, smooth, glistening, butyrous to slimy, of a cream color, 
and the medium is a uniform dark gray color. At the end of 20 days 
there is a decided odor of decay. There is feeble diastasic action on 
starch. 

Smith's potato starch jelly (5). — Growth moderate, diastasic action 
feeble, medium stained a light bluish green. Traces of dextrin. 

Starch agar. — To melted tubes of +10 beef-peptone agar sterile 
potato starch was added and plates poured. Tests with iodin showed 
no diastasic action. 

Litmus sugar agars. — One per cent lactose, maltose, dextrose, sac- 
charose, and galactose were used in beef-peptone litmus agar. Change of 
medium to a bright red showed considerable acid production with dex- 
trose and galactose; with saccharose there was less acid produced; and 
with lactose and maltose there was no evidence of acid production. Re- 
duction of litmus took place to a slight extent under the streaks with 
dextrose and maltose. 

Milk. — In fresh isolations a soft curd forms in from 5 to 7 days, fol- 
lowed by slow peptonization of the curd, which is completed in from 5 



150 Journal of Agricultural Research vol. xix,No. 4 

to 6 weeks. In old isolations curd usually is absent. The medium does 
not become viscid or slimy. The liquid at the top of the tube is some- 
times a yellowish green but more often brown. This brown color may be 
confined to a surface layer a few millimeters deep or may extend through- 
out the liquid medium. In old tubes the fluid is coffee-colored. It is 
unlike any color in Ridgway, but is somewhat like his moss brown. 

Litmus milk. — At room temperature the medium begins to turn 
slightly blue in 2 days, beginning at the top; and in 5 or 6 days it is fre- 
quently stratiform, being deepest blue at the top. Reduction begins at 
the end of a week, the tubes becoming cream-colored throughout, and 
clearing at the top or showing reduction only at the bottom of the tube 
for a depth of 1 cm. or more. There is no curdling, and clearing is com- 
plete in 2 weeks. At the end of 2 months the tubes are a deep blue-black 
and sometimes of a gelatinous consistency. At no time is there any red- 
dening. 

Methylene blue in milk. — In fresh isolations reduction begins in 
3 days and is completed in 7 days, except for a rim of blue at the top 1 
mm. deep. Curdling takes place in 1 week; peptonization begins soon 
after and is completed in 5 weeks, the clear liquid being yellowish to 
neuvider green, especially toward the top. 

Cohn's solution. — Growth is very slight, appearing in 24 hours and 
increasing slightly the second day. In a week clearing begins, and at the 
end of 3 or 4 weeks there is no clouding and only a little precipitate. 
Nonfluorescent. No crystals. 

Uschinsky's solution. — The medium shows light clouding in 24 
hours. In 48 hours a thin flocculent white film has formed over the 
surface and shakes down in fine particles. In 4 days there is moderate 
clouding, a slight surface film, and the medium is a pale turtle green. In 
2 weeks a heavy white rim has formed around the surface of the liquid. 
When the cultures are 6 weeks old there is considerable white precipitate — 
fluid, not viscid — and slides stained in carbol fuchsin show a network of 
long chains (PI. 34, C). Fluorescence persists in old cultures. 

Fermi's solution. — Light clouding occurs in 24 hours. In 4 days 
the're is moderate clouding and a delicate surface film which shakes down 
in fine flocculent particles. In 4 days as much growth as in Uschinsky. 
In 2 weeks the clouding is heavy, the medium has a greenish tinge, and 
there is a heavy white surface pellicle 2 to 3 mm. deep, which shakes 
down in strings of fine white particles. There is considerable white pre- 
cipitate — a heavy growth. In 3 weeks the white surface pellicle and the 
precipitate become cream-colored. No chains are formed. Greening 
first visible after about 2 weeks. At end of a month surface pellicle 
and precipitate tan color. Clouding and pellicle twice as abundant as in 
Uschinsky. 

LoEFFLER's blood serum. — Growth moderate, filiform to slightly 
undulate, flat, glistening, smooth, medium slightly browned beneath the 
streak. No liquefaction, not even after 2 months. 



May is, 1920 Halo-Blight of Oats 151 

Soyka's rice medium. — The growth and medium in all cases except one 
were cream colored. A culture marked "stock b" turned the medium a 
buff-pink. 

Nutrient broth plus carbon compounds. — To tubes of +10 beef- 
peptone bouillon 1 per cent asparagin was added and to other tubes 1 
per cent asparagin plus 1 per cent dextrose were added. The growth 
was equally good in both kinds of media. The organisms seem to obtain 
their carbon as readily from asparagin as from dextrose. 

Indol production. — Feeble or absent in beef-peptone bouillon or 1 
per cent peptone water containing 0.5 disodium phosphate and 0.1 mag- 
nesium sulphate. 

Hydrogen sulphid. — Hydrogen sulphid is not produced. Lead ace- 
tate paper suspended over broth cultures is not blackened, and the medium 
is unchanged when streaks are made on lead carbonate agar plates. 

Ammonia production. — Moderate. Made tests with Nessler's reagent. 

Nitrate in nitrate broth. — No gas is produced in fermentation 
tubes. Nitrates are not reduced. Tests were made at the end of 9 days 
and at the end of 2 months. 

Temperature relations. — The maximum temperature for growth, 
tested on beef broth and on agar and potato, is 31 ° C. The minimum 
temperature for growth is below o°. Tubes surrounded with ice showed 
clouding. The optimum temperature for growth is 24 to 25 . The 
thermal death point is between 47 and 48 . 

Moisture relations. — The organisms are very readily killed by 
drying. Smears were made from 5-day-old broth cultures to sterile 
cover glasses and placed in sterile Petri dishes. Pieces of these cover 
glasses transferred to sterile bouillon after 3 hours showed growth in all. 
All were dead at end of 24 hours. In a repetition, transfers after 6 hours 
gave no growth. 

Fermentation tests: (i) Potato juice. — Undiluted potato juice 
was expressed afte; passing the pared tubers through a meat grinder. 
Moderate clouding in open arm of fermentation tubes. No growth in 
closed arm and no gas. 

(2) Milk. — At the end of a week the milk at the open end had cleared 
without evident curdling. Two days later the milk in the closed end had 
curdled. This curd was gradually peptonized, about a third of it remain- 
ing at the end of 2 months. The cleared liquid in the open arm was 
browned — a chestnut to auburn brown at the surface and gradually 
changing to a lighter shade through the open arm and a third of the way 
up the closed arm. No gas was formed. 

(3) Carbon compounds. — Tests were made in the fermentation tubes 
with 2 per cent solutions of dextrose, saccharose, maltose, lactose, man- 
nit, glycerin, and levulose in 2 per cent water solutions of Difco's and 
Witte's peptones. Bacillus coli Escherich was used as a control and 
produced gas in the closed arm. The oat organism produced no gas and 



152 Journal of Agricultural Research vol. xix, No. 4 

did not grow in the closed arms of tubes containing maltose or lactose. 
In tubes containing saccharose, glycerin, and mannit there was growth 
at first only in the open arm, with a sharp line of demarcation between 
open and closed arms. At the end of a week clouding began to appear 
in the closed arms of tubes containing these three substances. In 3 
weeks there was light clouding throughout the closed arms in saccharose, 
moderate clouding throughout the closed arms in mannit, and in glycerin 
heavy clouding to within an inch of the top of the closed arm with light 
clouding on up to the top. In a later test there was again light clouding 
throughout the closed arms of tubes containing saccharose. In two 
later tests a moderate clouding appeared in the closed arms of tubes of 
saccharose and dextrose in from 4 to 7 days. In a later test of mannit 
and glycerin there was no ciouding in the closed arm. Tests for ammonia 
with Nessler's reagent gave a positive reaction in solutions of maltose, 
saccharose, mannit, glycerin, and lactose, but only traces of ammonia or 
negative reactions in cultures containing dextrose. Titrations with 
phenolphthalein as an indicator show a higher total titrable acidity in 
the cultures than in the controls in saccharose and dextrose. These 
solutions were also acid to litmus as compared with controls in two later 
experiments. The hydrogen-ion concentrations, determined after about 
6 weeks by the colorimetric method, were as follows: Control, P H = 4.8; 
dextrose, P H = 4.8; maltose, P H =7; saccharose, P H = 6.4; and lactose, 

P H =4-8. 

The organisms grew best in saccharose, levulose, and dextrose, 
showing heavy growth in the open arm and slight to moderate growth in 
the closed arm. This organism is evidently a facultative anaerobe 
when certain sugars are available. 

Toleration of acids. — Transfers were made to tubes of +10 beef- 
peptone broth containing 0.1 per cent and 0.2 per cent of citric, tartaric, 
and malic acids. There was good growth in 0.1 per cent of each acid 
but only slight growth or none at all in 0.2 per cent. 

Toleration of sodium chlorid. — Neutral beef-peptone bouillon con- 
taining, respectively, 2, 3, 4, 5, 6, and 7 per cent of sodium chlorid was 
inoculated from potato agar slants. There was slight clouding of 2 per 
cent after 3 days. None of the stronger solutions clouded, but slides 
made from a stringy white precipitate and stained with carbol fuchsin 
showed that long chains of cells had been formed in all strengths of sodium 
chlorid. A second test was made, using neutral broth with 0.5, 1, 1.5, 2, 
3, and 4 per cent solutions of sodium chlorid and inoculating from broth 
cultures. There was slight clouding in 1 per cent at the end of 2 days, 
slight clouding in 1.5 per cent at the end of 3 days, moderate clouding in 
1.5 per cent at the end of 5 days. At the end of 7 days there was slight 
clouding in 2 per cent and moderate clouding and a stringy swirl of pre- 
cipitate in 2 per cent at the end of 19 days. Stained slides of precipitate 
from 1.5 and 2 per cent solutions showed a network of long chains. In 
the second test there was no growth in solutions of more than 2 per cent. 



May is, 1920 Halo-Blight of Oats 1 53 

Optimum reaction and Toleration limits. — Beef-peptone bouillon 
was adjusted to each of the following reactions with sodium hydroxid 
and hydrochloric acid +20, +15, +10, +5,0, —5, —6, —13, —16, and 
— 22. These were uniformly inoculated from broth cultures and kept 
at 24 C. At the end of 24 hours there was light clouding in —5,0, +5, 
and +10. Subsequent clouding occurred in —6 and +15. A stringy 
precipitate formed in — 13, and on — 15 a thin surface film developed and 
the medium was slightly darkened. At the end of 48 hours the clouding 
in + 5 was slightly heavier than in +10, and the flocculent surface film 
slightly heavier. Clearing began in 3 weeks. At that time +10 was 
browned, +15 slightly deeper brown, and +5 and —5 showed a greenish 
tinge. The optimum reaction for growth is, therefore, + 5 Fuller's scale, 
although +10 and +15 are also favorable reactions. 

In later tests the limits of growth on agar were +27 and — 17, and in 
bouillon +27 and — 18, when the agar was reinoculated from an alkaline 
culture. 

Volatile acids. — Tests for volatile acids were negative. Cultures 
were grown in tap water containing 1 per cent Witte's peptone and 1 per 
cent dextrose. The steam from these cultures gave an alkaline reaction 
to litmus although the liquid was acid to litmus. 

Freezing. — Six plates were poured in +15 agar from 24-hour +15 
broth cultures. This 24-hour culture was exposed for 1 hour in salt and 
crushed ice and then six more plates were poured. Eighty-seven per 
cent of the organisms were killed by this treatment. 

Effect OF sunlight. — The organism is sensitive to sunlight; 80 per 
cent were killed by 15 minutes' exposure on ice in thinly sown beef- 
peptone agar plates. 

Vitality on culture media. — Typical colonies of this organism have 
been obtained from + 10 beef-peptone agar slants which have stood for 
11 months and from broth cultures 10 months old. These were tested by 
inoculation on young oat plants and gave abundant and typical halo 
lesions. 

Loss of virulence. — Loss of virulence on culture media has not been 
observed in cultures carried for more than 3 years. 

Group number. 1 — 221.2323023. 

The name Bacterium coronafaciens , n. sp., is suggested for this organism. 

TECHNICAL DESCRIPTION 

Bacterium coronafaciens, n. sp. 

A motile rod with rounded ends and polar flagella; single, in pairs or long chains, 
average measurement 2.3 by 0.65 n; no spores, zoogloea, or involution forms; capsules 
are formed; slightly facultative anaerobic. On nutrient agar colonies are white, 
round becoming irregularly circular, fiat with slightly raised margins, surface smooth 
or slightly contoured; deep colonies are lens-shaped and opaque. Its proteolytic 

1 Society of American Bacteriologists, descriptive chart. Indorsed by the society for general use 
at the annual meeting Dec. 31, 1914. Prepared by the committee on revision of chart identification of 
bacterial species. 



154 Journal of Agricultural Research vol. xix, No. 4 

power is moderate; gelatin is liquefied slowly, beginning in 2 days and not complete 
in 60 days; reduction of litmus occurs in milk, and the casein is digested without 
curdling; milk curdles in 5 days, and peptonization is completed in 5 weeks. No acid 
is produced in milk. Oxidations of proteins are incomplete; ammonia is produced ; 
hydrogen sulphid, gas, and indol are not produced. Nitrates are not reduced. There 
is slight diastasic action on potato cylinders. Good growth in Uschinsky's solution 
and in Fermi's solution. Growth in Cohn's solution is scanty. Maximum tempera- 
ture for growth is 31 C, minimum below o°, optimum 24 to 25 , thermal death point 
between 47 ° and 48 . Tolerates sodium hydroxid to —18 Fuller's scale and hydro- 
chloric acid to +27. The optimum reaction for growth is +5 Fuller's scale. Gram- 
negative, not acid-fast, stains readily and uniformly with gentian violet and methy- 
lene blue. Stains more or less irregularly with carbol fuchsin (often polar staining). 
Sensitive to drying; 87 per cent killed by freezing, 80 per cent killed by sunlight. 
Vitality on culture media long. Pathogenic on varieties of cultivated oats and to a 
slight degree on wheat, rye, and barley, producing oval halolike lesions of chlorotic 
tissue surrounding dead brown centers of infection. 

Beef-peptone agar and beef bouillon are favorable media for prolonged growth. 
Growth on potato agar brings out more distinguishing characteristics. 

II. — ISOLATION NO. 36 

This isolation was made from a halo lesion on oats obtained from 
Wooster, Ohio, in June, 191 7. It has the same group number as the 
stock halo organism just described but differs from it in the characters 
mentioned below. The differences, though not very marked, seem to be 
fairly constant, while the lesions from which the cultures were isolated 
and which they produce in inoculation work can not be distinguished. 
The stock organism seems to be slightly more virulent. 

Morphology. — The organism occurs singly or in twos but seldom in 
long chains (Pi. 34, A). Stained by Ribbert's capsule stain it measures 
from 1.1 to 3 ix in length and from 0.5 to 0.8 ix, in width, not including the 
capsule, with an average measurement of 0.66 by 2.1 /*. 

BEEF agar plates. — On +10 beef-peptone agar, the surface colonies 
remain round, and the margin tends to remain entire (Pi. 31, D). 

Potato-dextrose agar stroke. — Two-day-old slants from broth 
show moderate flatter growth, which is filiform and dull, with more or 
less wrinkling on the surface. The growth is somewhat translucent and 
of a butyrous to slightly membranous consistency (Pi. 30, B, a). 

Gelatin stab. — Liquefaction is more rapid, being complete in 40 days. 

Toleration of sodium chlorid. — Same as stock, but slides from a 
2 per cent solution stained with carbol fuchsin show only a few scattered 
short chains. 

Litmus milk. — Litmus is not reduced. 

Methylene blue. — Digestion of casein a little slower than with stock. 

Uschinsky's solution. — No chains on slide stained with carbol 
fuchsin. 

Cohn's solution. — Clouding heavier than with stock. Crystals are 
formed on the sides of the tubes. 

Starch agar. — The organism showed a feeble diastasic action on 
Starch. 



May is, 1920 Halo-Blight of Oats 155 

Temperature; relations. — Thermal death point is between 47 and 
48°C. 

Strain 36 usually gives a greenish tinge to bouillon cultures, which in 
old cultures contrasts strongly with the brown of old "stock" cultures. 
On ordinary beef-peptone agar the two strains can not be distinguished 
but on potato-dextrose agar there is considerable difference in amount 
of growth, and they are noticeably different in consistency. The most 
important differences perhaps are in size and in nonformation of chains. 
The rods of No. 36 are shorter and plumper. They seem to be two 
strains of the same organism. 

III. — YELLOW ORGANISM 

Morphology. — The organism is a motile rod with rounded ends and 
one to several polar flagella. It occurs singly or in short chains. When 
grown for 24 hours on beef-peptone agar and stained by the Duckwall 
modification of Pitfield method, it has an average measurement of 3.5 by 
1.4 ix, varying in length from 2.3 to 3.7 /*, and in width from 0.98 to 2.1 n. 
No spores have been found. 

Beef-peptone agar plates. — Colonies appear after 24 hours on 
+ 10 beef -peptone agar; in 2 days they measure 2 mm. in diameter and 
are a translucent light yellow. When a week old, surface colonies are 
circular, 4 to 5 mm. in diameter, raised, smooth, lemon-yellow, with 
entire translucent margins. Microscopically the internal structure is 
finely granular. Deep colonies are lens-shaped and opaque. 

Beef-peptone agar stroke. — Growth in two days is moderate, fili- 
form, flat, glistening, slightly contoured, translucent, light orange- 
yellow, with a faint odor. Consistency is butyrous, and medium is 
unchanged (Pi. 30, B, c). The organism lives at least three or four 
months on beef -peptone agar. 

Potato agar stroke. — In two days the growth is abundant, filiform, 
fiat, spreading, glistening, smooth, opaque, light orange-yellow. The 
medium is unchanged, and the consistency butyrous. 

Gelatin stabs. — At 22 ° C. growth in + 10 nutrient peptone gelatin is 
moderate. The liquefaction at first is saccate along the stab and later 
stratiform. Liquefaction is completed in 40 days. The surface growth 
has a pinkish tinge, but the precipitate is yellow. 

Beee-peptone broth. — There is moderate clouding in +10 beef- 
peptone broth in 24 hours at 25 C, very heavy clouding in 48 hours, 
and a slight flocculent surface growth. In 3 days there is a heavy mem- 
branous pellicle which breaks up when shaken and sinks to the bottoii 
of the tube. The precipitate is abundant and finely granular. Clearing 
begins in about 2 weeks. 

Toleration of sodium chlorid. — Tables of neutral beef-peptone bouil- 
lon containing respectively 2, 3, 4, 5, 6, and 7 per cent of sodium 
chlorid were inoculated from potato agar slants. In 24 hours there was 



156 Journal of Agricultural Research voi.xix,No. 4 

clouding in 2,3,4, and 5 per cent solutions. In 3 days there was a very 
slight clouding in 6 and 7 per cent solutions. A stringy yellow precipi- 
tate formed in the 4, 5, 6, and 7 per cent. Slides made from 2 and 3 
per cent solutions and stained with carbol fuchsin showed long chains 
of cells. There were no long chains in the 4, 5, 6, and 7 per cent. In a 
second test a delicate pink surface film, not previously observed, formed 
in 0.5, 1, 1.5, 2, 3, and 4 per cent solutions; and a pink stringy precipi- 
tate formed in 2 and 3 per cent, becoming a brick red in 4 per cent. 

Potato cylinders. — At 25 ° C. there was slight growth in 24 hours 
and a slight graying of the medium. In 4 days there was abundant 
yellow growth, and the medium had become slightly browned. Growth 
was filiform, flat, raised, glistening, somewhat contoured, orange-yellow 
to red on top. There was no odor, and the consistency was butyrous. 
There was no action on the starch. 

Milk. — Milk titrating +18 on Fuller's scale was inoculated from 9- 
day-old potato agar slants. A slight yellow surface film was formed in 

2 days. At the end of 1 week yellow precipitate was evident. Curdling 
began in 3 weeks. There was a slight separation of curd and whey at 
the end of 2 months. The solid curd gradually dried down without any 
evidence of peptonization. 

Litmus milk. — Complete reduction occurs in 24 hours, leaving the 
medium cream -colored. Shaking tended to restore the color. After 
about a week some of the reduced tubes were steamed, whereupon the 
original lavender color returned. Curdling occurred in 3 weeks. There 
was no evidence of digestion at the end of 2 months. 

Methylene blue in milk. — Reduction takes place in 24 hours. In 

3 weeks there is curdling and the blue color begins to return at the tops 
of the tubes. No petonization. 

Uschinsky's solution. — There is moderate clouding in 24 hours at 
25 C. and a membranous surface film. At the end of 2 days there is a 
fairly heavy light yellow surface film. In 4 days there is heavy clouding 
and a heavy surface film and yellow precipitate. Slides stained with 
carbol fuchsin show many short chains. 

Fermi's solution. — There is moderate clouding in 24 hours at 25 
C. In 2 days there is a fairly heavy light yellow surface film. In 4 days 
the clouding is heavy and there is a heavy orange-colored surface film 
2 mm. thick. At the end of a week this pellicle is 4 mm. thick. Clearing 
begins in 2 weeks, and yellow strands extend from the heavy pellicle 
to the bottom of the tube. At the end of 3 weeks the pellicle is 1 cm. 
thick. In 4 weeks the medium has a greenish tinge. No chains were 
observed on slides stained with carbol fuchsin. 

Cohn's solution. — There is a slight clouding at the end of 2 days at 
25 C At the end of 4 days the clouding is still very light, and there 
is just a trace of surface growth. Rhomboid crystals are formed on the 
tube above the liquid. Growth is very slight in comparison with that 
in Fermi's solution. 



May is, 1920 Halo-Blight of Oats 157 

Blood serum . — Growth was moderate, filiform, slightly raised, orange- 
yellow, smooth, shining. In 2 weeks the center of the growth became 
red, but the author was unable to verify this change in 191 9. The 
medium was unchanged. 

Litmus sugar agars. — In 24 hours there is a slight reddening of 
litmus dextrose agar and in 3 days reduction has begun in the lower end 
of the tubes, the upper two-thirds being rose red. Litmus-lactose and 
litmus-maltose agar show reduction in the lower ends of the tubes in 
3 days. These tubes are red through the center and blue at the top. 
At the end of a week all agars are colorless at the bottom of the tubes, 
red in the center, and blue toward the top. Growth is abundant. At 
the end of 2 weeks the colony begins to turn red. 

Starch agar. — There is no diastasic action on starch. 

Indol. — Indol production is feeble. 

Nitrate bouillon. — No gas is produced in fermentation tubes. 
Nitrates are not reduced. 

Ammonia. — Ammonia production is moderate. 

Hydrogen sulphid. — No hydrogen sulphid is produced. Tests were 
made with lead-acetate paper over broth and with lead-carbonate agar. 

Optimum reaction and toleration limits. — By the use of sodium 
hydroxid and hydrochloric acid, using phenolphthalein as indicator, 
beef-peptone bouillon was adjusted to each of the following reactions: 
+ 25, +20, +15, +5, o, —5, —6, —13, —15, and —22. These were uni-' 
formly inoculated from broth cultures and kept at 24 C. In 24 hours 
there was clouding in all except +20 and +25. At the end of 3 days 
there was clouding in all except + 25. The clouding in + 20 wa"s slight. 
At the end of 1 week there was no growth in +25, light clouding in 
+ 20, — 15, and — 22, and heavy clouding in all the other reactions, with 
precipitation and surface growth. In 3 weeks there was clearing in 
— 15 and —22, but a viscid yellow precipitate. There was never any 
growth in +25. The optimum reaction for growth is +5 Fuller's scale. 

Gas formation and aerobism. — Tests were made in fermentation 
tubes in the presence of the following carbon compounds: dextrose, sac- 
charose, lactose, maltose, mannit, and glycerin. A 2 per cent solution 
of each was made in a 2 per cent water solution of Dif co peptone. Bacil- 
lus coli Escherich was used as a control and produced gas in each solution. 
No gas was produced by the yellow organism. There was clouding in 
the open arm of all tubes in 2 days, the heaviest growth being in saccha- 
rose and maltose. In 3 days clouding began in the closed arm of tubes 
containing saccharose and mannit. At the end of a week there was 
clouding in the closed arm of all tubes — heavy in glycerin and mannit, 
light in dextrose, and moderate in the others. Tests for ammonia with 
Nessler's reagent gave a positive reaction in all sugars — slight in glycerin, 
and moderate in the others. Titrations with phenolphthalein as indica- 
tor showed no acid production. The hydrogen-ion concentrations were 



158 Journal of Agricultural Research vol. xix.no. 4 

determined by the colorimetric method at the end of 6 weeks. The P H 
for dextrose was for maltose 5 to 5.2, for saccharose 4.6, for lactrose 7, 
for glycerin 4.8, and for mannit 6. Controls and Bacillus coli Escherich 
showed a P H of 4.8 throughout. 

Temperature relations. — The maximum temperature for growth is 
above 38 C. The minimum temperature for growth is 3 . The 
optimum temperature for growth is 24 to 25 . The thermal death 
point is 48 to 50 . Tests were made by the same methods as those 
used for the halo organisms. 

Vitality on culture media. — The organism lives for 2 months on 
beef-peptone agar at room temperatures. It is nonpathogenic. 

Group number. — The group number is 221.3333533, according to the 
descriptive chart of the Society of American Bacteriologists. 

TECHINAL DESCRIPTION 

A motile rod, with rounded ends, one polar flagellum or several, single or occasion- 
ally in short chains; average measurement 3.5 by 1.4 a*; no spores, pseudozoogloeae, 
or involution forms; facultative anaerobic. On beef- peptone agar the colonies are 
round, raised, smooth, lemon-yellow with entire translucent margins; deep colonies, 
lens-shaped and opaque. Liquefaction of gelatin begins in 2 days and is complete 
in 40 days. There is reduction in litmus milk in 24 hours and delayed curdling with- 
out subsequent peptonization ; milk is curdled in 3 weeks without subsequent peptoni- 
zation; ammonia production moderate; indol production feeble; does not produce 
hydrogen sulphid or other gas; no diastasic action on starch; grows moderately in 
Uschinsky's solution, and very copiously in Fermi's solution. Growth slight in 
Cohn's solution. Maximum temperature for growth is above 38 C, minimum 3 , 
optimum 24 to 25 , thermal death point 48 to 50 . Tolerates sodium hydroxid 
to below —22 Fuller's scale, and hydrochloric acid to +20 Fuller's scale. The opti- 
mum reaction for growth is +5 Fuller's scale. Gram-negative; not acid-fast; stains 
readily with carbol fuchsin, gentian violet, and methylene blue. Nonpathogenic 
to oats. 

OVERWINTERING AND DISSEMINATION 

There is evidence from three sources that the organism causing halo- 
blight winters over on the seed: (1) the presence of typical halo lesions 
on the glumes and lemmas of maturing spikelets (Pi. 29) ; (2) the early 
appearance of the disease on seedlings grown on soil not previously 
sown to oats (PI. 28) ; and (3) the great difference in amount of blight in 
oat plots from treated and untreated seed. 

(1) natural and artificial infections of spikelets 

In 1 91 8 at the time the oat plants were heading out it became evident 
from observations of the plot of Wisconsin No. 14 and from artificial 
inoculation of Wisconsin No. 7 that the spikelets were also susceptible 
to infection with the halo organism. After the Wisconsin No. 7 plants 
had headed out a number of uninjured heads were sprayed with a water 
suspension of the organism. Another bundle of heads, bruised by draw- 
ing between the fingers, was similarly sprayed; and both were covered 
with glassine bags for two days. When the bags were removed infec- 
tions were already appearing on the bruised spikelets as light green 



May is, 1930 



Halo-Blight of Oats 



159 



discolorations on the glumes. A week after inoculation every spikelet 
of these panicles showed distinct typical halo lesions. Many halo lesions 
also appeared on the uninjured spikelets. Injured and uninjured con- 
trols sprayed with sterile water and treated in a similar way showed 
no halo lesions. 

Early in July natural infections on the spikelets of Wisconsin No. 14 
oats were observed. Flag leaves were found which showed either 
scattered halos or yellow halo tissue the length of the blade and sheath. 
Where sheaths surrounding the heads were badly haloed, every spikelet 
in the panicle showed infection. If there is one single lesion on a glume 
it appears as a typical light green to yellow halo about the point of infec- 
tion. When the whole glume is infected the tissue becomes yellow and 
translucent between the veins. Only a few such complete infections of 
panicles were found. Further observations showed that infections 
on a small percentage of the spikelets in a panicle were not uncommon 
even when there were no lesions on the sheaths below. Wind and rain 
might easily spread the infection directly from lower leaves to panicles. 
Isolations from the glumes showing these lesions and from the parts 
inside the glumes gave typical halo organisms. Table I, which records 
the counts on 42 panicles in one corner of a Wisconsin No. 14 plot, will 
give some idea of the percentage of blighted spikelets. 

Table I, — Number of blighted and blasted spikelets on oats naturally infected with 

halo-blight 



Panicle No. 



I 
2 
3 
4 
5 
6 

7 
8 

9 
10 
11 
12 
13 
14 

*5 

16 

!7 

18 

19 
20 
21 

32 

23 



Number 

of 
spikelets 

per 
panicle. 


Number 

of 
blighted 
spikelets 

per 
panicle. 


Number 

of 
blasted 
spikelets 

per 
panicle. 


58 


O 


6 


54 


O 


ir 


77 


I 


5 


66 


O 


14 


55 


O 


22 


55 





12 


55 





17 


60 





11 


42 





14 


64 


I 


13 


90 


2 


16 


5i 


I 


9 


61 


O 


22 


79 


36 


25 


18 


l8 


23 


87 


O 


4 


5° 


O 


13 


39 


O 


21 


54 


4 


34 


5° 


5 


35 


55 


2 


14 


62 





23 


69 





20 



Panicle No. 



24. 

25- 
26. 
27. 
28. 
29. 
3°- 
3* • 
32. 
33- 
34- 
35- 
36. 
37- 
38. 

39- 

40. 

4i- 

42. 



Total. 
Average . . . 
Per cent. .. 



Number 
of 

spikelets 

per 
panicle. 



67 

33 
80 

65 
45 
72 
85 
46 
SO 
55 
45 
7i 
65 
109 

52 
69 
66 
60 



2,387 
59+ 



Number 

of 
blighted 
spikelets 

per 
panicle 



O 

25 
o 
o 

29 

o 

5 
o 



165 

4 

6+ 



Number 

of 

blasted 

spikelets 

per 
panicle. 



17 
8 



14 

7 
10 

1 
o 

47 
8 

7 
4 

14 
6 
o 
8 
6 

13 



587 
14+ 
24+ 



160 Journal of Agricultural Research vol. xix.no. 4 

In this case 6 per cent of the spikelets are blighted. This accords 
with the percentage of primary lesions usually observed on seedlings in 
the field. The sheaths below the panicles numbered 15, 32, and 35 
were badly yellowed with halo lesions. 

(2) PRIMARY LESIONS ON THE FIRST LEAVES OF SEEDLINGS 

These primary lesions have been observed by the writer on more than 
30 varieties of oats in Wisconsin in two different years. They may 
appear as halos on any part of the leaf blade, but they more often occur 
on the tips or margins of the leaves as shown by Plate 28. 

(3) EXPERIMENTS WITH TREATED AND UNTREATED SEED 

During the season of 191 7 two plots of oats were planted on soil which 
had not previously been planted to oats. Untreated seed of each of 33 
Wisconsin varieties was planted in April, and in May seed of the same 
33 varieties was planted after having been soaked for 2% hours in 1 to 320 
formalin (1 pint to 40 gallons). Every one of the 33 varieties from 
untreated seed showed halo-blight to at least some extent, the amount 
decreasing as the hot weather came on. Wisconsin No. 14 showed the 
heaviest blighting, and Wisconsin No. 25 was also heavily spotted. 
Throughout the season not a single lesion was found on the 33 varieties 
from treated seed. 

In April, 1 91 8, three parallel plots of oats were planted on soil not 
previously planted to oats. Thirty-three Wisconsin varieties of 
untreated 191 6 seed were planted in the first plot, 44 Wisconsin varieties 
of untreated 191 7 seed were planted in the second plot, and 44 Wisconsin 
varieties of treated 191 7 seed were planted in the third plot. Also 
treated seed of Wisconsin No. 14 was planted as a fourth plot on the 
experimental ground where oats were grown in 191 7. This seed was 
treated by soaking for 3 hours previous to planting in 1 to 320 formalin. 

Counts of infections appearing in these plots were begun just as the 
second leaf was coming out. On May 16, 17, and 18 primary lesions were 
appearing on the first leaves of plots from untreated 1916 and 1917 seed, 
the number of primary infections varying from less than 1 per cent to 8 
per cent in each plot. These primary lesions on the 191 6 plot would indi- 
cate that the organism may live for two years on the seed. No lesions 
were found at this time on the plot from 191 7 treated seed. Counts were 
made again in the untreated 191 7 plots on May 25, four or five days after 
heavy driving rains, the normal incubation period for halo lesions. 
Practically all the first leaves were found to be spotted, and lesions were 
also appearing on the upper leaves. The condition in the 191 6 plot at 
this time was about the same and continued to parallel that of the 191 7 
plot. At this same time — 9 days after the first appearance of the disease 
on the untreated plots — scattered halo spots and yellowed leaf tips were 
beginning to appear on the treated plot, evidently by infection from the 



May is, 1920 



Halo- Blight of Oats 161 



neighboring untreated plots, one of which was only 3 feet away. On May 
24 and 25 there were more driving rains, and on the twenty-eighth the 
effects of these storms were evident. Secondary lesions in the untreated 
plots were so abundant that no attempt was made to count them. Many 
of the first leaves were completely yellowed and dead, and lesions on sec- 
ond and third leaves were so numerous that tips, margins, and even whole 
leaves were becoming yellowed. On varieties where infections were not 
so abundant the second leaves showed only scattered lesions. On the 
treated plot the primary lesions were still few, and there was here very 
striking evidence of the way in which the organism spreads about a center 
of infection. More or less circular spots of infected plants could be dis- 
tinguished with the more heavily spotted plants in the center. The 
amount of infection in this treated plot gradually increased until most of 
the first and second leaves showed some spotting, but in none of the vari- 
eties was there more than half as much blighting as in the untreated plots. 
In the third treated plot, Wisconsin No. 8 showed only scattered lesions 
on the lower leaves and none on the upper. In the untreated plot of this 
variety the lower leaves were practically destroyed and the upper so 
badly spotted that they showed a yellow-brown color at a distance. 
There were similar but less marked differences in other varieties. Through 
June there was very little rain. The amount of blight gradually de- 
creased until at heading time, about the first of July, very few halo lesions 
could be found, and the upper leaves were practically unspotted. 

No halo lesions were observed on the fourth plot from Wisconsin No. 
14 treated seed until about the twenty-fifth of the month, when two or 
three centers of infection began to appear as small yellow spots. These 
spread rapidly after each rain until one of them stood out as a distinct 
yellow spot irregularly 5 by 1 o feet in diameter. The plants in this spot at 
heading time were 4 or 5 inches shorter than the more normal plants 
about them and headed out about a week later. Subsequently scattered 
lesions occurred on lower leaves throughout the plot and undoubtedly 
came either from the first infections observed or from the neighboring 
plots. If these primary infections had been produced by soil organisms 
they would probably have been much more general. Either sterilization 
of seed was not complete or else the infection came from the neighbor- 
ing plots. 

An experiment with hot-air treatment of seed gave additional proof 
that the organism is seed-borne. A plot from Graber oats heated to 
ioo° C. for 30 hours showed no lesions throughout the season. There 
was not a single spot. The plot from untreated Graber oats showed an 
abundance of halo lesions through May and June. On every plant there 
was some spotting and many lower leaves were yellowed and dead. 

This early appearance of lesions on seedlings grown on new soil, the 
appearance of typical halo lesions on the glumes and lemmas of the 



l62 



Journal of Agricultural Research 



Vol. XIX, No. 4 



developing spikelets from which the halo organism was isolated, and 
finally, the absence of the disease on plants from sufficiently treated seed 
all lead to the conclusion that this is a seed-borne disease. 

HOSTS OTHER THAN OATS 

Field observations and artificial inoculation experiments indicate that 
the halo-blight organism of oats does not readily infect other hosts. No 
halo lesions similar to those appearing on oats have been observed in 
the field on wheat, barley, corn, or timothy. In Jefferson and Dodge 
Counties, Wis., fields of oats and barley were planted so close together 
that the plants were intermingled at the margins. In both places the oat 
plants were heavily spotted with halo lesions, but even where these spotted 
oat leaves came in contact with the barley leaves not a halo could be 
found on barley. At Arlington Farm, Va., one halo lesion was found on 
a rye plant growing among infected oat plants, but no plates were made. 
The field was half oats and half rye, and although practically all the oat 
plants were spotted no other lesions could be found on rye. 

Six different sets of inoculation experiments were carried on in the 
greenhouse during the winter of 1917-18 to test the pathogenicity of 
the halo-blight organism on wheat, rye, barley, and corn. The methods 
of inoculation were the same as those described above. The organisms 
used were stock and No. 36. The results are given in Table II. 

Table II. — Inoculations on other plants with halo-blight from oats 



Wheat 

Rye 

Barley 

Spelt 

Corn 

Oats, Wisconsin 14. 
Controls 



Experi- 
ment I, 
stock. 



+ + + 



Experi- 
ment II, 
stock. 



Experi- 
ment III, 
stock. 



+ + + 
+ 



+ + + 



+ 
+ 



+ + + 



Experi- 
ment IV, 
stock. 



Experi- 
ment V, 
stock. 



+ 



+ + + 



+ + + 



Experi- 
ment VI, 
No. 36. 



+ + 

+ 
+ + 



+ + + 



+ Slight infection. 
+ + Moderate infection. 



+ + + Heavy infection. 
— No infection. 



Halo lesions were obtained on wheat in two different experiments, in 
the second of which the halo lesions were not so large but almost as 
numerous as on oats. 

In three out of six experiments halo lesions were produced on rye. In 
the first, infection was so heavy that there was a general wilting of the 
leaves. Typical white organisms were isolated from these leaves which 
on reinoculation produced halo lesions on oats but not on rye. 

Halos on barley were obtained in three out of six inoculation experi- 
ments. There were eight halos in the first experiment and two in the 
second. In the third experiment, six leaves had one or more halos. 



May is. 1920 Halo-Blight of Oats 163 

Reisolation from the first halos gave typical white colonies which on sub- 
culture and reinoculation produced halos on barley and oats. 

No halos were obtained on corn in four experiments, and no halos were 
obtained on broom corn in later experiments. Oat plants inoculated at 
the same time always showed abundant infection. It is evident that the 
halo-blight organism may attack wheat, rye, and barley to a slight 
extent; but in Wisconsin, at least, halo lesions in the field rarely, if ever, 
appear on anything but oats. 

VARIETAL SUSCEPTIBILITY 

All observed varieties of cultivated oats are attacked by the halo-blight 
to some extent. Wisconsin No. 14, both in the field and in the greenhouse, 
is more susceptible than any other variety and shows more lesions in 
later stages of development, especially on the flag leaf, rachis, and spike- 
lets. Two varieties, Wisconsin No. 13 and Wisconsin No. 15, grown in the 
fields on either side of Wisconsin No. 14 during 1917, showed considerable 
resistance. Although leaves of Wisconsin No. 14 were badly spotted, the 
leaves of Wisconsin No. 13 and 15, which came in contact with them, 
showed little spotting. In the first plot (from 191 6 untreated seed), 
described above, Wisconsin No. 128 showed only six primary infections, 
while Wisconsin No. 124 showed 169. In the second plot (from 1917 
untreated seed) some varieties showed only slight secondary infections, 
others moderate, and some heavy infection. 

Inoculation experiments in the greenhouse also brought out differences 
in varietal resistance. Wisconsin No. 1,5, and 14 were used for several 
experiments, Wisconsin No. 14 always showing so much heavier infection 
than either of the other two that Wisconsin No. 1 and 5 were no longer 
used. Wisconsin No. 1 showed more resistance to infection than Wis- 
consin No. 5. 

While certain varieties are more susceptible than others under ordinary 
conditions and show fewer primary lesions at the beginning of the season, 
as above indicated, the differences are not marked in severe blight years 
as the season advances. 

RELATION OF ORGANISM TO HALOED TISSUE 

The oval outline of the halo, its rapid spread from the point of infec- 
tion, and the fact that the haloed tissue remains normal, apparently, 
except for loss of color, have led to the conclusion that the discoloration 
is probably due to some diffusible substance produced by the bacteria 
rather than to their immediate presence. To determine whether or not 
the bacteria were equally distributed throughout the lesions, isolations 
were made from pieces of tissue cut from the centers of lesions and from 
points at varying distances from the center as shown in the following 
diagrams. Isolations were made after treatment with mercuric chlorid 
as described above. The distribution of bacteria throughout the halo 
lesions is shown in Plate 33 and Table III. 



164 



Journal of Agricultural Research 



Vol. XIX. No. a 






V, 



^ 

§ 



^ 



S 



ft! 



•4 

pg 

< 






I I 



+ + 



I I 



+ °. 





T ° 

+00 



1 1 



1 l 



++ 
++ 



GO 



May is, 1920 Halo-Blight of Oats 165 

The first two lesions used were produced by artificial inoculation. The 
last three were natural infections from the experimental plots. In all 
of the five isolations only the plates from the centers of the lesions 
showed any growth at all, and these plates were heavily seeded with 
typical white colonies. The only exception is the one colony on a plate 
from isolation IV, section 2. In isolation I the broth cultures from sec- 
tions outside the center did not even cloud. In other isolations where 
broth cultures from sections outside the center clouded, subsequent 
plates showed that the clouding was sometimes due to the growth of the 
halo organism and sometimes to contamination. 

The bacteria are evidently abundant only in the centers of the lesions, 
and if any do occur outside in the halo they are very few in number. 
This indicates that the discoloration of the halo-tissue is due only indi- 
rectly to the presence of bacteria, and that some enzym or toxic by- 
product destroys the chlorophyl. A suggestion of what this by-product 
might be was obtained from some plates of potato-dextrose agar on 
which colonies of the blight organism were growing. When colonies 
of the stock organism were 3 days old distinct halos appeared in the agar 
about the colonies as illustrated in Plate 32, B. The agar around these 
colonies was less translucent than that outside the halos and was dis- 
tinct in outline. These halos in the agar increased in diameter from day 
to day, showing the concentric circles of growth illustrated in the plate 
and characteristic of the lesions on oat leaves. Acetic acid dropped on 
the agar-plate halos cleared them in a minute or two. Drops of am- 
monium carbonate [(NH^COJ and ammonium chlorid [NH 4 C1] on 
sterile plates of the same potato agar produced in a few minutes halos 
similar in size and appearance to those produced by the colonies of 
bacteria. Acetic acid also cleared these halos. Litmus was added to 
melted potato agar at the rate of one drop of a saturated solution to 10 
cc. of the agar, and plates were poured. Streaks of stock were made 
across the agar as soon as it had hardened. Similar streaks on plain 
potato agar produced distinct halos about them in two days. In the 
same time the litmus potato agar had turned a distinct blue for 1 cm. 
or more on all sides of the growth. It seems probable, therefore, that 
the ammonia produced by the blight organism is responsible for the 
destruction of the chlorophyl and for the halolike lesions produced in 
the oat plants. 

Stained sections of haloed leaf tissue also show bacteria only in the 
center of the lesion. The bacteria at first are intercellular, but later 
they destroy the cell walls and cause the collapse of the tissue. The 
collapsed tissue is evident as the dead brown centers of lesions. (See 
H. 35, C.) 



1 66 Journal of Agricultural Research vol. xix,n .4 

COMPARISON WITH OTHER SIMILAR BACTERIAL DISEASES 

Seasons of excessive rainfall and of abnormal conditions in the oat 
fields similar to those of 191 8 have been recorded for 1890 and 1907-8. 
For the earlier record we are indebted to Galloway and Southworth, of 
the United States Department of Agriculture (1), and for the later work 
to Thomas F. Manns, of the Ohio Experiment Station (j). 

WORK OF GALLOWAY AND SOUTHWORTH 

In 1890 Galloway and Southworth (/) published a preliminary note 
on what they termed "a new and destructive oat disease." This disease 
appeared in May and June of that season and was so widespread and 
severe as to threaten to destroy the entire oat crop of the eastern and 
central States. The signs described were a browning of the tips of the 
lower leaves, which spread until in a short time all the leaves were dead 
and brown. Bacteria were found in these lesions. The account of the 
disease by these authors, however, is too meager to afford any basis for 
judgment as to whether or not it was the disease here described. 

During the seasons of 1906- 1909 blade-blight of oats was recorded again 
over a fairly wide area, and in 1907 it was so severe in some fields as to 
occasion a loss of from one-half to two-thirds of the crop. In 1908 the 
blight was threatening at one time but eventually caused little loss. 
The accounts of the disease from southern Canada and central and eastern 
States are of the same general kind. They mention a general yellowing 
of the lower leaves of young plants, the yellow color changing to a brown 
or red under weather conditions unfavorable to the organism, such as a 
sudden change from cool, cloudy weather to bright sunshine and higher 
temperature. The fields are often described as having a rusted appear- 
ance because of this reddening of the blades. The trouble was attributed 
to various causes — to insects, to bacteria, to fungi, and to unfavorable 
weather conditions. 

In 1908 Dr. Erwin F. Smith discovered this disease at Arlington Farm, 
Va., photographed it, cut sections, and made cultures of the organ- 
ism on various media, but did not publish upon it nor make any inocu- 
lations, although it is quite certain from the type of the disease and the 
nature of the cultures that he had the same organism here described. 
This was perhaps its first isolation in pure culture. 

No other serious research work was undertaken until Thomas F. Manns 
carried on his investigations during the seasons of 1908-9 at the Ohio 
Experiment Station. 

WORK OP THOMAS F. MANNS, I906-I909 

Manns (3) states that — 

the disease manifests its presence by changes in color varying from a light yellowing, 
which apparently checks but little the growth of the oats, to a pronounced redden- 
ing, which in severe cases kills the blades, leaving only the younger leaves and the 
central axes alive. 



May is. 19=0 Halo-Blight of Oats 1 67 

The primary yellowing sooner or later changes to a mottled red or brown. 
In another place he says: 

The preliminary effects of this disease is a yellowing, beginning either as small, 
round lesions on the blade, or as long, streak lesions extending throughout the blade or 
even the whole length of the culm and blade. Occasionally it begins at the tips and 
works back into the culm; again the upper leaves often break down through a weak- 
ened condition of the plant from defoliation below. 

When lesions work back from the leaves to the culm a general yel- 
lowing and collapse of all the foliage may result. In 1909 — 

the disease in the majority of infected leaves began as small yellow spots on different 
parts of the blades. When these points of infection were numerous, the infected areas 
quickly became confluent, and the collapsed leaf showed a brownish mottled appear- 
ance. 

These brief statements are the only references in the bulletin (exclu- 
sive of PI. XIII) to anything at all corresponding to the lesions char- 
acteristic of the blight here described, and there is much that is contra- 
dictory. His colored figures as well as most of his text indicate an entirely 
different disease, but his Plate XIII shows that this halo-disease formed 
at least a part of the phenomenon under consideration. The distinct 
reddening which he describes and which he illustrates in Plates X and 
XI was not observed anywhere in Wisconsin even in the worst blight 
year, 191 8. A distinct reddening of oat leaves was observed in our 
plots but was not due to the halo-blight. Two unsuccessful attempts 
were made by the writer to isolate bacteria from these reddened leaves. 
Manns attributes the severity of the outbreak in 1907 to the abnormally 
low temperatures of April, May, June, and July and to the unusual 
amount of rainfall during those months and gives convincing climato- 
logical data in support of his conclusion. He states that the results 
of artificial inoculation in the greenhouse also support this theory that 
cool, humid weather conditions favor the disease. 

Through isolation and inoculation experiments Manns came to the 
conclusion that the blade-blight of oats was due to two species of bacteria 
living in symbiotic relations within the host tissue (Pseudomonas avenae 
Manns and Bacillus avenae Manns). His isolations were made by ster- 
ilizing the blades in 2 to 1,000 mercuric chlorid solutions for 1 to 1% 
minutes and following this by four washings in sterile water. He states 
that in practically all isolations from diseased oats these two bacteria 
were found to be more or less abundant, and when occurring together 
they could be plainly seen on the agar poured plates in from 2 to 3 days. 
The yellow organism {Bacillus avenae Manns) always appeared first. 
As a rule, the white organism predominated. 

Inoculations were made by Manns in several ways: (1) Directly 
from crushed leaves; (2) by hypodermic injection, using separate pure 
cultures of the white and the yellow organism; (3) by hypodermic in- 
jection, using the two cultures mixed (3, PI. X); (4) by spraying mixed 



1 68 Journal of Agricultural Research voi.xix,No. 4 



cultures on injured and uninjured leaves; (5) by root inoculations with- 
out wounds, using mixtures of the two organisms; and (6) by means of 
grain aphids. 

He reports that inoculations in the field and in the greenhouse showed 
that the yellow organism when used alone produced no lesions and that 
the white organism when used alone produced only "limited and non- 
typical lesions," which formed slowly, extended from ^ to 1 inch from 
the point of infection, and then remained checked. When a mixture of 
the two organisms was used the lesions appeared in from 10 to 12 days 
and spread rapidly. From these results he concludes that the disease 
is a symbiosis, the white organism requiring the presence of the yellow 
organism to be actively pathogenic. 

He also states that the virulence and viability of the white organism 
on artificial culture media depend greatly upon association with t«he 
yellow organism and that the pathogenic action of the white organism 
was more marked when carried over winter in mixed culture with the yel- 
low organism than when carried over separately. After nine months 
in pure culture t'he white organism failed in several instances to grow. 

Manns sta'tes that endospores occur. These were stained with hot 
carbol fuchsin from 2-months-old cultures. The figure of these spores 
in his Plate IX is too indistinct to be of any value in verifying his state- 
ment. 

His white organism is described as a short motile rod with polar 
flagella. These are three to five times the length of the rods in his 
Plate IX, fig. 4, and one to six times those in his text figure No. 1. The 
rods measure in the majority of cases 0.75 by 1.5 ju. They are rarely 
in chains of three to four. 

The thermal death point is 6o° C. The optimum temperature is 20 to 
30 . He states that his organism is pathogenic on oats, corn, timothy, 
barley, wheat, and bluegrass. 

The group number for his white organism is given as 11 1.2223032. 
Manns' yellow organism is a bacillus with the group number 222.2223532. 

Manns suggests the probability of the organism's wintering over in the 
soil and so being distributed to the leaves by spattering rains. He 
states that there is no doubt that on seedlings lesions sometimes start 
on the roots or on that part of the stem in contact with the soil. He 
does not describe these lesions. The possibility that the disease is seed- 
borne is not mentioned. 

Manns' descriptions of individual lesions are so meager and his descrip- 
tions of general signs so inclusive as to lead to grave doubt about his hav- 
ing worked with a single bacterial disease. There is no doubt, however, 
that he sometimes had typical halo-blight lesions, because of his Plate 
XIII, but with this exception there is no conclusive evidence from either 
his text or figures that he had this disease under observation; and the 



May is, 1920 



Halo-Blight of Oats 



169 



result of his inoculations as indicated on his colored plates is quite con- 
tradictory. 

The chief differences between the two white organisms Pseudomonas 
avenae Manns and Bacterium corona faciens, n. sp., are summarized 
below : 



6. 



PSEUDOMONAS AVENAE MANNS. 

Produces typical blight lesions only 
when used with Bacillus avenae 
Manns (a yellow organism). 

Spreads throughout the lesion when 
used alone. 

Virulence and viability on artificial 
media dependent upon association 
with Bacillus avenae Manns. 

Viability and virulence greatly re- 
duced by a number of transfers. 

Growth feeble on artificial media. 
(See 3, PL VIII, fig. j.) 

Liquefaction of gelatin stabs begins in 
7 to 12 days. 

7. Pitting of gelatin colonies begins in 7 

days. 

8. Visible growth in broth in 3 days. 

9. Manns does not record browning of 

broth or other media. 

10. Milk not coagulated in 30 day 3. 

11. Acid to litmus milk. 

12 . No reduction of litmus milk recorded. 

13. Strictly aerobic. 

14. No ammonia produced. 

15. Nitrates reduced. 

16. Limits of growth, —5 to +15. 

17. Thermal death point 6o° C. 

18. Internal structure of agar colonies 
amorphous. 

In hanging drop there are few motile 

organisms. 
Growth viscid on agar. 
Produces Clostridium forms in one 

week on nutrient glucose agar. 

22. Produces endospores. 

23. Does not form long chains. 
Shorter and thicker than Bacterium 

coronafaciens. Average size 0.75 by 

i-5 M- 
Lives over in the soil. 
26. Pathogenic on oats, corn, timothy, 

barley, wheat, and bluegrass. 
Group number 11 1.2223032. 



IQ 



20. 
21. 



24. 



BACTERIUM CORONAFACIENS, N. SP. 

i. Produces typical halo-blight lesions 
when used in pure culture. 

2. Found only about the point of infec- 

tion and not throughout the halo. 

3. Virulence and viability not dependent 

on another organism. 

4. Viability and virulence not reduced 

by transfer. 

5. Growth abundant on artificial media. 

(See PI. 30, A, B, a, b.) 

6. Liquefaction begins in 3 days. 

7. Pitting begins in 3 days. 

8. Visible growth in 1 day. 

9. Broth and other media turned brown. 

10. Milk usually coagulated in 5 to 7 days. 

11. Alkaline to litmus milk. 

12. Litmus milk reduced. 

13. Facultative anaerobic. 

14. Ammonia produced. 

15. Nitrates not reduced. 

16. Limits of growth, —18 to +2 7. 

17. Thermal death point 47 to 48 C. 

18. Internal structure of agar colonies not 
amorphous. (See PI. 31.) 

Active motile organisms in hanging 

drop. 
Growth butyrous. 
No Clostridium forms observed in any 

medium. 
Does not produce endospores. 
Forms chains and long filaments. 
Average size 0.65 by 2.3 /*. 



19 



23- 
24. 



25 



25. Lives over winter on the seed. 

26. Pathogenic on oats, barley, wheat, 
and rye. 

Group number 221.2323023 

A bacterial disease producing lesions similar to those of the halo-blight 
of oats has been described from tobacco (10). The lesions are similar to 



170 



Journal of Agricultural Research 



Vol. XIX. No. 4 



the halos of oats in that they form "circular chlorotic areas" 2 to 3 cm. 
in diameter with minute brown centers. The oat lesions, however, have 
no water-soaked borders, and the affected tissues do not fall out as in 
tobacco wildfire. A white organism has been isolated from these lesions 
which differs from the halo-blight organism in the points mentioned 
below : 



HALO-BUGHT ORGANISM. 



One to several polar flagella. 

Single to long chains. 

2.3 by 0.65 fx. 

Capsules. 

Odor in agar stroke. 

Casein not precipitated in litmus milk. 

Ammonia produced. 

Thermal death point 47 to 48° C. 



TOBACCO ORGANISM. 



One polar flagellum. 

Single to chains of five elements. 

3.3 by 1.2 p. 

No capsules. 

No odor in agar stroke. 

Casein precipitated in litmus milk. 

Ammonia not produced. 

Thermal death point 65 ° C. 



The halo lesion so characteristic of this oat disease does not occur in 
the blackchaff disease of wheat (6-9) or the bacterial blight of barley 
(2), while the oat disease lacks the translucent water-soaked stripes 
of these diseases as well as the exudate so abundant in both. R. H. 
Rosen has recently published a preliminary note on a bacterial dis- 
ease of foxtail (4), which he thinks may be similar to the halo-blight 
of oats. His description of lesions as dark brown spots or streaks, 
however, makes it probable that if it is similar to either bacterial disease 
of oats it would resemble stripe-blight rather than halo-blight. The 
writer has not observed halo lesions on foxtail and in two sets of field 
inoculations has obtained no infections on foxtail with the halo organism. 

CONTROL MEASURES 

The evidence that the halo-blight of oats is seed-borne seems conclu- 
sive. However, no practical method of seed treatment has, as yet, 
been found which will entirely control the disease. Treatment with 
formalin for smut controls halo-blight to a marked extent but not entirely. 
In 1917, treated seed of 33 Wisconsin varieties did not show a halo lesion 
throughout the season, while the same untreated varieties all showed 
some halo-blight. In 1918, 44 treated varieties of Wisconsin oats devel- 
oped primary lesions which, however, were later and fewer than on the 
same untreated varieties. Even when the blight was most severe it 
was only about half as heavy in the treated plots as in the untreated. 
The plot from Wisconsin No. 14 treated seed showed very few primary 
lesions and little secondary spotting except in patches about these pri- 
mary lesions. This would indicate that soaking for three hours in 1 to 
320 formalin kills many but not all of the organisms on the seed. In 
Jefferson County, Wis., where most of the seed was treated for smut, the 
blight during the 191 8 season was much less abundant than in Dodge 
County, where seed treatment was not general. 



May 15, 1920 Halo-Blight of Oats 171 

Another method of seed treatment is being developed at Wisconsin 
which in 191 8 entirely controlled halo-blight. The treated seed was 
heated in a gas oven at ioo° C. for 30 hours. The plot from this treated 
seed did not show a single halo lesion even during the time when other 
oats were most severely attacked. The plot from untreated seed of 
the same variety showed primary infections on 10 per cent of the plants 
and 100 per cent secondary infections on the lower leaves during May 
and the first two weeks in June. While oats in good condition success- 
fully withstand this treatment of 30 hours at ioo° C, a similar treatment 
for a shorter period would perhaps be just as effective. The commercial 
application of this treatment has not as yet been worked out. 

SUMMARY 

A bacterial disease known as halo-blight was unusually severe in its 
attack on oats throughout Wisconsin during the 191 8 season, and reports 
of a similar disease were received from southern Minnesota, Iowa, north- 
ern Illinois, and Indiana. Such epidemics occur under particularly 
favorable weather conditions, disappearing with the advent of weather 
conditions more favorable to the development of the host plant. 

Typical lesions of halo-blight are characterized by halolike margins 
of chlorotic tissue about a center of dead tissue. 

Isolations from these lesions have constantly given a typical white 
organism. Yellow organisms also appear from isolations when the surf- 
ace of the tissue has not been sterilized. 

Inoculation experiments have shown conclusively that the white organ- 
ism alone is responsible for the production of typical lesions. The yellow 
organism is evidently a surface saprophyte. 

Since few if any organisms are found outside the central infection area, 
the halo is thought to be due to a diffusible substance, probably am- 
monia. 

The organisms live over winter on the seed, producing primary lesions 
on the first leaves of seedlings. From these lesions the organisms are 
carried to other leaves by wind and rain. 

It seems probable that the percentage of blasting on oat panicles 
varies with the severity of the halo-blight from season to season. This 
blasting seems to be due to the same unfavorable weather conditions 
which favor the development of the bacterial blight rather than to the 
disease itself. 

Halo-blight lesions from natural infections have never been observed 
on any hosts except oats and rye. Artificial inoculations show that the 
halo organism may be slightly pathogenic on wheat, rye, and barley. 

When the halo-blight is not too severe, different varieties of oats show 
differences in susceptibility to the disease. 



172 Journal of Agricultural Research vol. xix, No. 4 

The organism isolated and described by the writer has the group 
number 221.2323023. No other white organism used by the writer 
has produced anything similar to the halo lesions. Other white organ- 
isms have in fact produced no lesions on oats. Three strains of softrot 
organisms with internal markings very much like those of oat colonies 
have been used, and also the white organism, Bacterium atrofaciens McC, 
which produces lesions on wheat. The name of Bacterium coronafaciens 
n. sp. is suggested for this white halo-producing organism. 

Treatment with 1 to 320 formalin, as for smut, checks but does not 
entirely control the disease. A hot-air treatment for 30 hours at ioo° 
C. does control the blight. 

LITERATURE CITED 

1) Galloway, B. T., and Southworth, E. A. 

1890. PRELIMINARY NOTES ON A NEW AND DESTRUCTIVE OAT DISEASE. In 

Jour. Mycol., v. 6, no. 2, p. 72-73. 

2) Jones, L. R., Johnson, A. G., Reddy, C. S. 
1917. bacterial blight OP barley. In Jour. Agr. Research, v. 11, no. 12, 

p. 625-644, illus., 4 pi. (1 col.). Literature cited, p. 643. 

3) Manns, Thomas F. 

1909. THE BLADE BLIGHT OF OATS, A BACTERIAL DISEASE. Ohio Agr. Exp. 

Sta. Bui. 210, 167 p., illus., 15 pi. Literature cited, p. 166. 

4) Rosen, H. R. 

1919. A preliminary note on A bacterial disease OP foxtail. In Science, 
n. s. v. 49, no. 1264, p. 291. 

5) Smith, Erwin F. 

1905. bacteria in relation to plant diseases, v. 1. Washington, D. C. 
(Carnegie Inst. Washington Pub. 27.) 
6) 

7) 



1917. black chaff of wheat. In U. S. Dept. Agr. Bur. Plant Indus. 
Plant Disease Survey Bui. 2, p. 40. 



1917. A NEW disease of wheat. In Jour. Agr. Research, v. 10, no. r, p. 51-54. 
pi. 4-8. 



8) 

1918. black chaff OF wheat. In U. S. Dept. Agr. Bur. Plant Indus. Plant 

Disease Survey Bui., v. 2, no. 6, p. 98-99. 

9) Jones, L. R., and Reddy, C. S. 

1919. THE black chaff of wheat. In Science, n. s. v. 50, no. 1280, p. 48. 

10) Wolf, F. A., and Foster, A. C. 

1918. tobacco wildfire. In Jour. Agr. Research, v. 12, no. 7, p. 449-458, 
illus., pi. 15-16. 



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PLATE C 

Halo lesions on flag leaves of Wisconsin No. 14 oats. Natural infections from Hill 
Farm, Madison, Wis. Photographed June, 1917. 



PLATE 26 

Typical isolated halo lesions. Natural infection on Graber oats. Photographed 
June 24, 1918. Natural size4 



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PLATE 27 

Halo lesions on Wisconsin No. 14 oats produced by spraying with a water suspen- 
sion of the stock organism May 26, 1917. Photographed May 31, 1917. 



PLATE 28 

Infe&tion from untreated 1916 seed of Wisconsin No. 124 oats. Planted April 24, 
1918. Photographed May 17, 1918. 



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PLATE 29 

Spikelets of Wisconsin No. 14 oats: 

A. — Left and center spikelets show natural infection with halo-blight. Tips 
yellowed and translucent. Spikelet at right normal, unspotted. Photographed 
July 17, 1918. 

B. — Upper spikelet shows typical isolated halo lesion near base. Lower spikelet 
normal, unspotted. 



PLATE 30 

A. — Two per cent +5 glucose Difco peptone beef bouillon agar slant of No. 36. 
Three-day colony. Photographed August 29, 1919. Natural size. 

B. — Two per cent potato-dextrose agar slants, a, No. 36, white culture, consistency 
butyrous; b, stock, white culture, consistency of boiled starch; c, No. 39a, yellow 
culture. 



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PLATE 31 

A. — Three-day colony of stock on 2 per cent dextrose-potato agar. Photographed 
February 17, 1919, by oblique transmitted light. X 10. 

B. — Two-day colonies of stock on + 10 beef-peptone agar. Photographed March 26, 
1919, by oblique transmitted light. X 10. 

C. — Five-day colony of stock on potato-dextrose agar. Colony of boiled starch 
consistency. Photographed January, 1918, by reflected light. X 7. 

D. — Five-day colony of No. 36 on + 10 beef-peptone agar. Photographed October 
1, 1918, by oblique transmitted light. X 10. 

E. — Three-day colony of stock on 2 per cent glucose Difco peptone beef bouillon 
agar. Photographed October 7, 1919, by oblique transmitted light. X 10. 

F. — Seven-day colony of stock on -f 1 5 beef -peptone agar. Photographed March 3 1 , 
1919, by oblique transmitted light. X 10. 

G. — Margin of 3-day colony of stock on + 15 gelatin. Photographed September 30, 
1919- X 75- 



PLATE 32 

A. — Five-day colonies of stock on potato-dextrose agar. Colonies of boiled starch 
consistency. (For single colony see PI. 31, C.) Photographed by reflected light, 
Natural size. 

B. — Three-day colony of stock on potato-dextrose agar. Halo about colony. 
Photographed February 17, 1919, by oblique transmitted light. X 5. 



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PLATE 33 

Isolations from sections of halo lesion. The lesion was from an artificial inocula- 
ion with oat stock organism made February 25, 1918. Isolates were made March 
k, igi8 on potato agar. The sections were dipped in alcohol and then submerged 
for one minuTe in 1 to 1,000 mercuric chlorid. The plate from secUon c xs the only 
one showing colonies of bacteria. 

A.— Poured plate of isolation from section a of lesion. 

B — Poured plate of isolation from section b of lesion. 

C— Poured plate of isolation from section c of lesion. 

D— Poured plate of isolation from section d of lesion. 

E— Poured plate of isolation from section e of lesion. 

Photographed March 15, 1918. 



PLATE 34 

A. — No. 36 from 24-hour potato-dextrose agar slant; carbol fuchsin stain. X 620. 
B.— Stock from 24-hour potato-dextrose agar; Ribbert's capsule stain. X 620. 
C. — Stock from 4-day potato-dextrose agar; carbol fuchsin stain, showing long 
chains. X 620. 

D. — Stock from 3-day potato-dextrose agar; Ribbert's capsule stain. X 1.550. 
E. — Stock from i-day + 15 beef-peptone agar; Van Ermengem stain. X 1.550. 
F. — No. 36 from i-day + 5 beef-peptone agar; Caesar-Gil stain. X 1,550. 



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PLATE 35 

Sections of oat leaves through halo lesions, showing bacteria in the tissues. Fixed 
in Gilson's fixative and stained with carbol fuchsin. 

A. — Bacteria in substomatal cavity, showing method of entrance of bacteria into the 
leaf tiasue. Cut 15 n thick. X 700. 

B. — Bacteria in substomatal cavity. Cut 15 n thick. X 1, 650. 

C. — Section of older lesion, showing bacteria between the cells. In the upper 
part of this section the tissue is disintegrating at about the point of infection. 

Photographed August 26, 1919. X i>55Q- 



WUSk 




